1. Field of the Invention
The present invention relates to the transmission of heated fluid and particularly to the delivery of "hot blast" air from a source to a shaft furnace. More specifically, this invention is directed to segmented conduits, such as tuyere stocks, which are utilized to conduct heated fluids and especially to hermetic expansion joints for employment between the segments of such conduits. Accordingly, the general objects of the present invention are to provide novel and improved methods and apparatus of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention has been found to be particularly well suited for use as a compensator connection between serially arranged conduits which are provided with an inner refractory lining. Such lined conduits are employed, for example, in tuyere stocks for the delivery of hot air to a blast furnace. In the environment of a tuyere stock the fluid passing through the lined and serially arranged conduits may be heated to temperatures up to 1400.degree. C. The compensator connections or expansion joints between the conduits must, accordingly, be hermetic and additionally must permit thermally induced expansion of the conduits.
Continuing with a discussion of the environment of a blast furnace, it is conventional for such furnaces to be provided with an external circular conduit, known in the art as a "bustle pipe" or "hot blast" conduit, which receives preheated air from a heat exchanger known as a hot blast stove. This bustle pipe extends around a furnace and the heated air, also called the "hot blast", is delivered therefrom for injection into the furnace via a plurality of segmented conduits, known in the art as tuyere stocks, located on the periphery of the furnace. The tuyere stocks generally comprise a plurality of serially coupled conduits which are provided with a refractory lining. A tuyere stock is customarily rigidly coupled, at its upstream end, to a fitting on the bustle pipe by means of a flange or other similar connecting device. In order to absorb or compensate for manufacturing, assembly and installation tolerances, and particularly to compensate for deformations and distortions which occur during use, some or all of the conduits which comprise the tuyere stock are interconnected by means of expansion bellows, spherical swivel articulations, Cardan compensators or other similar expansion joint defining devices. These expansion joint defining devices or compensator connections permit the intermediate conduit or conduits of the tuyere stock to move with respect to the conduit which is rigidly connected to the "bustle pipe" and with respect to the tuyere or nozzle which projects through the furnace wall. For economic and safety reasons, such movement must occur without escape of the heated fluid beng conducted through the tuyere stock.
A known tuyere stock which includes expansion joints of the universal coupling or "Cardan" compensator type is disclosed in U.S. Pat. No. 3,662,696. The Cardan compensators of U.S. Pat. No. 3,662,696 offer the advantages that differential deformations of the individual conduits, resulting from the high temperature of the air being delivered to the furnace, are compensated by means of bellows which have a limited number of corrugations and without utilization of ball-and-socket joints.
In the tuyere stock of U.S. Pat. No. 3,662,696 the blast nozzle of the tuyere stock is pressed firmly against the blast tuyere in the furnace wall in the conventional manner through the use of suitable clamping devices. Thus, in U.S. Pat. No. 3,662,696 the contact between the nozzle, which is the downstream section of the tuyere stock, and the tuyere is defined by a spherical sealing surface which compensates for any relative displacements between the nozzle and tuyere. Tuyere stocks of the type shown in U.S. Pat. No. 3,662,696 generally employ a first pair of coupling compensators in a first linear portion between the bustle pipe and an elbow section, which couples the substantially linear upstream portion of the stock to the nozzle, as well as the third articulated or swivel joint in the vicinity of the furnace wall such as, for example, between the nozzle and the blast tuyere or between the nozzle or the blast tuyere and the wall of the furnace. Tuyere stocks of the general type disclosed in U.S. Pat. No. 3,662,696 are thus known in the art as "three hinged" stocks.
Tuyere stocks of the "two hinged" type are also known. In the latter type of "hot blast" transmission conduit the nozzle portion of the tuyere stock is rigidly connected to the blast tuyere in such a manner that the refractory internal lining within the nozzle and tuyere is substantially continuous. In the use of such "two hinged tuyere stocks" means must be provided to maintain the integral nozzle and tuyere in a preselected position relative to the wall of the furnace. This requisite position maintenance, in turn, results in the absence of an articulated connection at the furnace wall. The resultant necessary forced guidance or support of the nozzle, which does not allow any lateral movement, requires the employment of compensators which can absorb or compensate for both angular deviation and longitudinal displacement; such compensators being incorporated between the individual segments of the tuyere stock which are located between the elbow and "bustle pipe". Compensation for both angular deviations and longitudinal sliding displacements may be obtained through the use of universal coupling connections provided with elongated slots on the hinged arms thereof; such slots limiting longitudinal displacements in two directions and facilitating the assembly of the tuyere stock. A tuyere stock of the "two hinged" type is shown in pending U.S. patent application Ser. No. 339,117 which is assigned to the assignee of the present invention.
To briefly summarize the state of the art, in conduits intended for use in the transmission of very hot fluids, for example in tuyere stocks, an expansion joint is provided between the refractory internal lining of adjacent serially arranged conduit sections. A corrugated or bellows-type compensator is disposed around the expansion joint and connected to the adjacent conduit sections in order to seal the joint therebetween from the surrounding atmosphere while compensating for deformations of the conduit sections resulting from thermally induced expansion. The corrugated or bellows-type compensators are the components of a compensator connection most susceptible to damage and, particularly in the case of a tuyere stock for a blast furnace, these elements must be shielded from the heated fluid passing through the conduit. In order to obtain the requisite thermal shielding, resort has previously been had to defining, by means of the refractory lining material of the conduit sections, a cascaded joint and filling such joint with a refractory and compressible special mineral wool. Alternatively, sperical joints have been provided between adjacent conduit sections.
In the design of a hermetic expansion joint, and particularly a joint between the refractory internal linings of adjacent conduits of a tuyere stock, two conflicting design requirements are observed and the resulting expansion joint is necessarily a compromise between these two conflicting requirements. The first requirement is the necessity of minimizing the width of the joint so that the bellows are not directly exposed to the heated fluid being conveyed and to avoid the occurrence of a hot air whirl. The second requirement is the need to make the joint sufficiently wide so as to obviate the possibility of contact between the facing refractory linings; any such contact impeding the movements which the compensator is intended to absorb and also causing damage to the linings.
Although the above briefly described expansion joints or compensator connections have been successfully employed, and offer a satisfactory solution to the above-discussed design compromise, it has nevertheless been recognized that improvements in such expansion joints were warranted in order to facilitate relative movements of the individual conduit segments and/or to enhance the shielding of the bellows of the compensators.